Process of recovering combined ammonia from gases.



H. L. DOHBRTY.

PROCESS PQR REGOVERING COMBINED AMMONlA FROM GASES'.

APPLICATION FILED FEB.15, 1910.

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. H. L. DOHERTY. PROCESS FOR REGOVEMNG GOMBHQBD Mmmm. FROM GASES.

APPLICATION LEE) FEB.15,1910.

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H. L. DOHERTY. PROGESSEOR REGOVERING COMBINED AMMONIA FROM GASES.

APPLICATION FILED FEB. 15, 1910.

Mgfgm@ Patented Nov. 5, 1912.

3 SHEETS-SHEET 3.

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f ammonium sulfate.

HENRY L. DOHEBITY, OF NEV YORK, N. Y.

PROCESS FOB RECOVERING COMBINED AMMONIA. FROM GASES.

Lila-3,210.

Specification o1.' Letters atent.

Patented Nov. 5, 1912.

Application tiled February 15, 1910. Serial No. 544,094.

To all whom, 'it may concern.:

Be it known that I, HENRY L. DOHERTY, a citizen of the United States, and a resident of New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Processes for Recovering Combined Ammonia from Gases, of which the following is a specification.

My invention relates to a process -for recovering combined ammonia from gases, and, in particular, to such a process in which the ammonia is fixed by either or both sulfur acids derived from sulfur compounds of the ammonia-bearing gases or by the carbon dioxid of said gases. Thus I fix the ammonia of the gases by chemical.substanceswhich occur as impurities in the ammonia-bearing gases and, inthe case of coal gases, are formed contemporaneously with the ammonia itself.

In my copending application Ser. No. 544,095, filed Feb. 15th, 1910, I have described and claimed a modification of the herein-revealed invention.

The object of my invention is to provide a process, whereby the alnmonia occurring in industrial gases such as the gases from the destructive distillation of coal may be converted into a salt consisting, usually, chiefly of ammonium sulfite mixed with ammonium sulfate and some ammonium carbonate, by means of sulfur acids formed from the sulfur of the hydrogen suld (or other sulfur compound) formed during the manufacture of the gas, and the carbon dioxid likewise formed, when the sulfur content of the gases is not sufficient to fix all of the ammonia. This lat-ter condition may obtain, in practice, chiefly in producer gases made by the various processes of gasification. In the distillation gases from coal, the sulfur content of the gases is usually more than suflicient to fix all ofthe ammonia.

In the usual manner of fixing the ammonia formed in the distillation or gasification of coal, the ammonia-bearing gases are conducted through a suitable chamber in which they are contacted with separately manufactured sulfuric acid, fixing the ammonia as This product is used as the source of ammonia for various industrial purposes but, chiefly, as a fertilizer. By my method, I am able to fix the ammonia in a form that is just as available as the sulfate without the necessity of using any chemical reagents other than those obtained from the coal at the same time as the ammonia.

Briefly, my invention consists in absorbing the ammonia, hydrogen sulfid and carbon dioxid of the gas in a partially purified ammonia liquor containing a substantial proportion of its ammonia in the free or hydrated condition, separat-ing again from the foul liquor formed by contacting the partially purified liquor with the crude gas, a proportion of its ammonia and acid gases ((102 and I-IzS) approximately corresponding to the quantity of such constituents which the liquor had absorbed from the crude coal gas, adding sufficient oxygen to said separated gases to oxidize the hydrogen sulfid contained therein, conducting the mixture of separated gases and air through a bed of iron oxid (or other suitable cat-.1-

lytic material) maintained at a reactive temperature, whereby the hydrogen sulfid in said gases is oxidized to form water vapor, sulfurous and sulfuric anhydrid, and cooling the gases after their passage through said catalytic material, whereby there is rccovered a mixture of ammonium sulfite and sulfate.

In the accompanying drawings, Figure 1 is a perspective view of the gas cooling and scrubbing apparatus. Fig. Q is a detail of the same showing how the scrubbing liquor passes from compartment to compartment of said apparatus. Figs. 3 and G, taken togetherz show in part a diagranmiatic elevation and 1n part a section of the apparatas for separating theammonia and sulfur gases from the scrubbing liquor and making the fixed ammonia salts therefrom with the heat interchanger shown in part section. Fig. 4 is a detail of the still shown in Fig. 3. Fig. 5 is a vertical diamctral section through the heating compartment l2 and upper part of the boiling compartment. 18 of the still shown in Fig. il.

In the drawings, 1 is the absorption apparat-us. rI`his is divided into a plurality7 ot compartments, a, l), c, d, e, f, g and h, in the design shown, each con'ipartmcnt having located above it a compartment (2M 2b, 2c, etc., respective1y,) in which is a eooling coil (3 3b, etc.,) through which the liquor used in the compartment, to wash the gas, is passedfor the purpose of cooling it, before introducing it into the compartment 1n contact with the gas. The cooling is performed, in the apparatusshown, by the circulation of a cooling liquid around the coils in the compartments 2. Circulating pumps, 4 4b, etc., maint-ain a constant circulation of liquor from t-he bottoms of the compartments to the `respective cooling coils. After passing through the coils 3,.

the liquor passes through some suitable distributing device, which should secure a uniform distribution of the liquid across the crosssection of the compartment. In Fig. 1 is shown a part perspective of the distributing device for chamber a. This distributing device comprisesa tray. 60,', having a perforated bottom 61,. The aggregate area of the perforations should be such relative to the volume of liquor circulating that there will always be a substantial depth of liquor on the bottom 61 of the tray 60,. Any variation in the rate of circulationiof the liquor is automatically taken care of by the increased rate at which the liquor passes through 61 with the increase in head ot liquor in xx and vice versa by the diminution of ilow with the fall of head in 60,. The sheet. 62a forms the top of compartment a and at the same 'time the bottom of the cooling `compartment 2,. As shown, the liquor enters the middle portion of thecoil 3 and iowing each way, discharges through the respective connections 63,l and 64@n 'on to the distributing tray 60 and thence passes through the'perforations `of the bottom 61l into the chamber a. The method of distribution of the scrubbing liquid is the same in all of the compartments. These compartments, a, b, c, etc., generally contain a structure of grids or trays over the surface of which the liquid finds its way to the bottoms of the compartments to be again circulated through the respective cooling coils and the compartments. The surface of the grids (or whatever form of tilling is used) is thus kept constantly wetted. The gas passes through the interstices of the grid structure and is thus brought into intimate contact with the scrubbing liquid.

In compartment h, the gas which, here, should contain only a trace of NH3, and the acid gases, I-IZS, CO2, are subjected to scrubhing by a portion of reviously formed ammonia li uor, which as been freed, in the manner (hereinafter described, from substantially all of its volatilizable compounds which is conducted to the compartment h through pipe 7. The extent to which it is necessary to remove the volatilizable nases from this portion of the liquor dependas, in great measure, upon thetemperature that prevails in h. While ammonia has'a considerable alinity for water, even weak solutions ot'Nlln in water possess an appreciable vapor tension, at ordinary temperatures. It is necessary that the liquor used Vfor scrubbing in 71, should have a vapor tension of its NH3 less than the tension of the small uantity of NI-I3 in the gas passing througi compartment z. Usually, the finaltraces of NH3 are removed from the gas by scrubbing with fresh water. By my method, however, I prefer to use liquor that hasbeen freed from its volatile anim'onia in'order to avoid the dilution of the liquor that is occasioned by the use ot fresh water. The liquor in h, is maintained in circulation by pump 4h, as already explained. A. ortion of this liquor', corresponding to tie volume of fresh liquor introduced through pi e 7, overflows to compartment g, throng the sealing device shown on an enlarged scale in Fig. 2, and mixes lwith the liquor circulating in compartment g.

The sealing device shown is formed by two baiiies, 8h and 8,z respectively, spaced away from the wall dividing i from g. The lower part of the dividing wall is pierced with numerous apertures 65. Under normal conditions of working the liquor level in the bottom of compartment L would be at considerable height above the batlles 8h` andSg-say at the level RS. Since in normal working a portion of the liquor is constantly 'withdrawn from one of the compartments-d for examplc-the level ot liquor in this compartment tends to tall. This causes a iiow of liquor from the next communicating compartment e, through a sealing device similar to the one described above, lwhich in turn causes a iow of liquor from f to e and so on. Owing to the friction ofthe gas passing through the compartments and the connecting ports, there is a slight graduated tall in pressure at a given level in each of the compartments trom 0, to z. For this reason, the difference in level of the liquor between any two a lja cent compartments is greater than that which would be required to produce the necessary flow of liquor from compartment to compartment were the gas pressures in the adgacent compartments equal. This is indicated by the line T-U of F ig. 2, which may be taken to indicate the liquor level in compartment g.

The liquor is introduced to g by the pipe 9, connected, in the arrangement shown, to the suction pipe, 5g, of pump 4g, and is circulated in the manner described, a volume of liquor corresponding to the overlow from l1. and the quantity of purified liquor introduced through 9, overflows to compartment f. The liquor flows in this way from compartment to compartment, a volume being maintained in circulation in each compartment much greater than the volume of the flow from compartment to compartment. The volume of liquor supplied through the pipes 7 and t) depends, in great measure, upon its content of tree ammonia. lt is necessary to introduce in the liquor supplied through 7 the quantity of free'ammonia that will sutlice, 1n connection with the ammonia already present in the gas, to form suld and carbonate, respectively, with the H28 and CO2 of the foul gas. When the proper quantity of free ammonia is supplied in the liquor, substantially all of the H2S, C()2 and NH, is removed from the foul gas. In my preferred method of working, I withdraw the liquor bearing the I-IQS, ()2 and NH3 from compartment (l, through pipe 10, and run it to the ammonia salt recovery plant. This is shown, diagrammatically, in Figs. 3 and 6.

11 is the still in which the impurities removed from the gas are separated again from the liquor, and about one-half or more of the ammonia in the latter again converted to the free or hydrated condition. 11 has in its lower portion three heating chambers, 12, 13 and 14. Upon the uppermost of these chambers, l2, is built up the still proper. This is composed of a plurality of sections, 151, 152, 153, etc., arranged as shown in Fig. 4.

16 is a lieater-cooler, or heat-interchanger, consisting of a cylindrical tank having an upper and lower tube-sheet (17 and 18, respectively,) with tubes 66 supported thereby. The chamber, included between the tubesheets, is divided, by partition 19, into two compartments, 16 and 16". The liquorpassing through pi e 10, which contains the NIL, H23 and O., absorbed from the gas, enters 16 below the tube-sheet 18 and passes up through the tubes 66 to the space above the upper tube-sheet 17. During its upward passage through the tubes, the liquor is heated by two streams of hot liquor passing in the reverse direction through the compartments 16 and 16". Now the ammonium suld of the liquor begins to dissociate at a temperature as low as 98 Fah. although complete dissociation is effected only at a much higher temperature. The ammonium carbonate begins to dissociate at about 124 Fall. Some dissociation, therefore, takes place even in the heater-cooler, with the evolution of H. .S and CO2. This dissociation of the ammonia salts causes an appreciable absorption of heat which is rendered latent and thus increases the thermal capacity of the foul liquor with a consequent increase in the eilicicncy of the heatercooler. The gases evolved from the liquor in the course of this heating discharge from 16 through the ipe 2O into thepipe 31 carry ing oit the e uent gases from 11. The heated liuor from 16 enters the uppermost section 15 as shown). From 15t3 it overflows from section to section through the sealed overflow passages 21 into the upper heating compartment 12. As the liquor passes through the sections 15, it is subjected to the action of the hot gases discharging from the compartment 12. More of its ammonium sulfid and carbonate are therefore decomposed with the evolution from the liquor of the hydrogen sultidand carbon dioxid of the salts so decomposed. The hot gases from 12 which bubble through it, while eliminating part of the ILS and C02 from the foul liquor at the same time give up the larger portion of the NIL, which they carry, to the liquor, since the ailinity of thev NIL, for the water is much stronger than that of the other gases, mentioned. The heat absorption attendant upon the dissociation of the ammonium salts assists materially in the cooling of the eflluent gases from 12. In the heating chamber 12, the liquor is heated to a temperature that is, preferably, from 6 to 12 degrees below the boiling point of water, at the ressure prevailing in 12. This pressure, o course, depends upon the altitude of the locality in which the process is being carried out and upon the back pressure caused by the liquid seals in the compartments of the still.

I aim to carry on the operation in 12, as stated, at a. temperature varying from 6 to 12 degrees below the boiling point of water under the pressure prevailing in 12. For example, if the barometric pressure in 12, is about 25.9 inches of mercury I would preferably maintain the temperature at about 197 to 198 Fall., while at a baroinetrie pressure of, say, 31.3 inches in 12, I would preferably heat the liquor therein at a temperature of about 204 Fah. While purification can be effected considerably below this temperature, I find the rate of purification at a lower temperat-ure so slow that, ordinarily, I do not consider it advisable to use temperatures lower than those given, although the separation of the foul gases and the ammonia may be thereby made with less loss of ammonia in the one operation. At this range of temperature, 19T-204, the decomposition of the ammonium sulfid and carbonate is very rapid. The freed foul gases pass oil very rapidly from the liquor, setting up a pseudo ebullition. A portion of the ammonia also passes oil with the foul gases, the carrying ol'f of the ammonia bcing, iu part, mechanical. The greater part of the ammonia liberated in tie dissociation of the ammonium salts is retained in the liquor owing to the relatively great absorption coeflicient of water -for ammonia, at even the temperature prevailing in 12. The liquor discharging from 12 is divided into two streams; the main stream is drawn oil' from 12 through pipe 23, and forced b v pump 24e to the to of compartment 16 of icater-cooler 16. he other stream is permitted to pass through the overflow 12 into the boiling compartment 13. The liquor after passing through 12, will have had about to (50% of its original HZS and CO2 eliminated, with a loss of only about 8% of its ammonia.` The residual ammonia is present as free or hydrated ammonia to the extent of about 50 to 55% of the total. By decreasing the velocity of How, it is possible to increase this proportion of free ammonia, but. at the expense of the production of a weaker liquor.` Therefore, I have found thatl the method of working outlined 0ives the most economical results. I aim to drive ofl` from the liquor in- 11, just about the proportions ot' ammonia aud acid gases, Which correspond to the increments of those gases, which are received by the liquor in passing through the gas washer 1.

In compartment 13, the ortion of the purified liquor from 1Q, whici passes thereinto, is subjected to active boiling, until the NHM C()2 and H2S have been, substantially, completely driven off. The evolved gases, together with the steam generated, pass through the liquid in 19. through a sealing device shown iii Fig. 5. The gases from 13 pass up through the vapor pipe 40 under the hood t1. The pressure builds up under the hood until the liquor sealing the perforations 4Q, in the flange of the hood 41, has been depressed sufficiently to unseal the perforatioiis 42, when the gases pass through -f2 and bubble up through the body of liquor in 1Q, which absorbs` part of the contained aiiinionia from the gases, increasing its strength and purity. The unabsorbed p0rtion of these gases passes in admixture with the gases driven off in 12, through the li uid seals iii the upper sections. Part of the IUI, evolved in lis taken up again by the liquor in 12, but the C()2 and HZS pass through without being absorbed owing to the temperature in 12. The boiled liquor discharging from Hi is subdivided into two streams, one being drawn ofi' through pipe 25, and raised hy pump 26 to the top of com )urtnient lo. The other subdivision o the liquor passes through the overflow, 27, into the liiiiing compartment, 14. The liquor leaving li contains only the fixed salts of ainomnia-sulfate, chlorid, etc. The proper quantity of milk of lime is run into 14, through the pipes E28, to combine with the acid of the fixed ammonium salts and liberate their NIL. This YHn passes up through the pipe 2!) into the vapor space of 13, and ljoins the gaseous current discharging from 13. The liquor discharging from 14, which has been freed from all of its ammonia, both volatile and fixed, is permitted to run to waste through the pipe 67. The cooled liquor discharging from compartment 1G', passes directly .to the circulating pump of compartment liy through the pipe 7, where'it is used to remove the inal traces of ammonia from the gas. lt then enters compartment g and joins the main stream of purified liquor entering that compartment. The efiiuent gases from 11, containing the NH3, CO2 and HES evolved from the foul liquor flowing to 11, pass through the pipe 31, to blower 352. On the suction pipe of blower 32 is an air damper 33, through which the proper quantity of air is admitted to the gaseous current, passing through 31, to furnish the oxygen necessary to oxidize the sulfur of the HQS in the gases. The mixture of still gases and air next passes to the oxidizing chamber 3-1. This contains a bed of iron oxid, or some similar material, 35, supportedby a grate, 3G, the oxid being maintained, preferably, at or below an incipient red heat` In passing through the bed of oxid (or other similarly reacting material) the hydrogen sulfid of the gas current is oxidized to water and sulfurous and sulfuric anhydrid, the former greatly redominating. The reactions which take p ace with the oxid are cyclic in character, and, it is not necessary to consider them, the final result may be represented by the following equations, viz.:

(a.) 2H,s+so,=ernoieso2 (b.) QSOLOFQSO,

The pro ortion of SO, formed is relatively sina l, most of the sulfur being oxidized to SO2. -While gaseous NHn, unmixed with any substance which has the property of forming a stable com-pound with 1t, is dissoeiated in the presence of heated oxid of iron to form water, free nitrogen and some nitrogen oxid, in the present case it is protected to a great extent by the SO.` and SO3 formed. These com-bine with the ammonia to form ammonium sulfite and sulfate, which remain suspended in the gaseous current as a heavy fume. After )assing` through 35, the gases are conducted t iroiigli 37 to a series of settling chambers, 88, 38, etc., where the fume is deposited on the walls and floor of the chambers and may be removed at intervals through the doors 3i). lVhen the sulfur gases present are sufficient to combine with all the ammonia the salt formed will consist rineipally of ammonium sulfite mixed with some bisulfite and sulfate. Some carbonate of ammonia will also be formed if the temperature of condensation is sufficiently low to permit of its formation. On the other hand, if there is a deficiency in the sulfur compounds present, the ammonium carbonate will be proportionally high. In this case, the temperature to which the gases are cooled in the condensation must be much lower than in the former case. Therefore I prefer, in this oase, to supplement the condensing apparatus by a supplementary condenser, 4:6. The sulfur salts of ammonia are separated from the gas in the chambers 88. The operation is, preferably, so arranged that the elihient gases from 3S.have a temperature somewhat above that; at which the ammonium carbonate lforms, say 15()0 Fall. The gases from 38 bearing the ammonia not condensed as a. sulfur salt in 38, together with the carbon dioxid and water va or, etc., are forced by blower 47 to the cham er 48 of condenser 46. rlhis condenser is of a common type and any equivalent device may be substituted for it. The gases pass from chamber 48 up through the opening 49 under-the erforated dome 50 in chamber 51. Tiliey bubble through the perforations in 50, through the liquor in 51, and on up through the sections 59., 58, etc., above. A mother liquor saturated by the ammonium salt is continuously circula-ted through the sections of 46 by the pump 55. The cold liquor cools the 'gases taking up the ammonium carbonate salt which, owing to the saturation of the liquor, immediately crystallizes out as the so-called sesquicarbonate of am-monia. The crystals work down with the liquor through the sections of 4G and are run out with the liquor through pipe 56 over the tine screen 57 lin tank 58. This screen retains the crystals, which may be removed at intervals. The strained mother liquor collects in the bottom of 58 and is drawn oft by ump 55 and forced through a cooling coi 59, to the top of 46, to be again passed therethrough.

Of course if preferred, a dry condenser may be used for the ammonium carbonate; but, I have found, that in separating this salt from an excess of diluent gases, it is ditiicult to secure a complete recovery of the ammonia by dry condensation.

Having described my invention, claim is 1. The process of recovering salts of ammonia from crude gas which comprises separating the contained ammonia, carbon dioxid and sulfur gases from the crude gas by absorption in a liquid separating the said gases from said liqui subjecting the said separated sulfur gases to oxidation in the presence of the said ammonia and recovering the salts of ammonia so formed.

2. The recess of recovering salts of ammonia rom crude gas which comprises separating the contained ammonia, carbon dioxid and sulfur gases from the crude gas by absorbing the. said gases in a liquid, separating the said gases from said liquid, and oxidizing the said sulfur gases to a mixture of sulfurous and sulfuric anhydrids in the presence of said ammonia to form oxidized salts of ammonium.

3. The process of recovering salts of ammonia from lan ammonia-and-sulurbearing gas which' comprises separating the ammonia and lsulfur constituents from the crude gas, contacting the said 'separated ammonia and sulfur constituents of the gas what I with a metallic oxid maintained at a reacting temperature, recovering the soformed iixed sulfur salts of ammonia, and re-oxidizing said metallic oxid.

4. The process of making fixed ammonia. salts containing a major proportion of ammonium sultite, which comprises separating the ammonia, carbon dioxid and sulfur constituents of a crude gas from the said gas, adding to the se arated gases sufiicient oxygen to oxidize t ie sulfur of the same to sulfur dioxid and causing a reaction to take place between the sulfur containing gas and said oxygen in the presence of the ammonia of the said gases and recovering the fixed ammonium salts so formed.

5. The process of making ammonium sulite which comprises separating the contained ammonia and hydrogen sultid from a crude gas, adding to the separated gases suflieient oxygen to oxidize the hydrogen sulid of the same to sulfurous anhydrid and water and passing the resulting gaseous mixture in contact with a suitable catalytic material, whereby ammonia of said gas mixture is converted into ammonia sultite.

6. The process of making oxidized sulfur salts of ammonia which comprises separating from a crude gas the ammonia and sulfur gases which it contains, adding to the separated gases sufiicient oxygen to oxidize the hydrogen sulfid of the same to sulfurous anhydrid and water and contacting the so-formed gas mixture with oxid of iron, whereby ammonia of said gas mixture is converted into oxidized sulfur salts of ammonia.

7. The process of making oxidized sulfur salts of ammonia which comprises separating from a crude gas, the ammonia and sulfur gases which it contains, adding to the separated gases suiiicient oxygen to oxidize the hydrogen sulfid of the same to sul-furous anhydrid and water, contacting the soformed gas mixture with oxid of iron at approximately an incipient red heat, wherebv ammonia of said gas mixture is converted into oxidized sulfur salts of ammonia.

8. The process of making oxidized sulfur salts of ammonia which comprises separating from a crude gas, the ammonia and sulfur gases, which 1t contains, adding to the separated gases sufficient air to furnish the oxygen re uired to oxidize the hydrogen sulfid of tie same and water, contacting the .so-formed gas mixture with oxid of iron at approximately an incipient red heat to oxidize the said hydrogen suliid to water and a mixture of to sulfurous anhydrid sulfurous and sulfuric anhydrids eontaining both substances in substantial proportions, combining the said ammonia with the said oxidized sulfur gases to `torni oxidized sulfur salts of ammonium, and subjecting the residual gases containing the .so-formed vammonium salts to cooling .to separate the Y said liquid to treatment to eliminate therefrom the ammonia, carbon dioxid and hydrogen sulid separated from said crude gas, .subjecting the gases eliminated from said liquid to an oxidizing action of such character that the sulfur of the contained hydrogen sulfid is oxidized while the contained ammonia remains substantially unoxidized` and combines with the oxidized compounds oi' sulfur formed and water, to forni fixed salts of ammonia.

10. The process of recovering oxidized sulfur salts of ammonia from crude gas which comprises contacting said with a liquid capable of absorbing the ammonia and hydrogen suld of said crude gas, whereby the said constituents are separated from said gas, withdrawing said liquid from contact with said gaasubjecting said liquid to hegting to4 eliminate therefrom the aniinonla and hydrogen sultid separated from said crude gas, contacting the separated ann monia and hydrogen' sultid with a i'netallic oxid which will yield up part of its oxygen to oxidize said hydrogen snltid to water, vsulfur dioxid and sulfur trioxid which, in the presence of the ammonia, combine with the latter to form ammonium sultite and sulfate.

11. The process of recovering oxidized sulfur salts of ammonium from crude gas which comprises contacting said gas with a liquid capable of absorbing the ammonia and hydrogen sulfid ot said crude gas, whereby the s'aid constituents are separated from said gas, withdrawing said liquid trom contact with said gas, subjecting said liquid to heating to eliminate therefrom the ammonia and hydrogen sulfid absorbed by said liquid from said crude as, contacting the separated ammonia "an hydrogen sulfid with oxid of iron maintained at a temperature such that it will gire up par-t of its oxygen to oxidize said hydrogen sultid to water, sulfur dioxid and sulfur trioxid which, in the presence of said ammonia, combine with the latter to form ammonium suliite and sulfate, restoring to said iron oxid the oxygen ,given u by the same to said hydrogen sulsulfur; salts of ammonium from crude gas whiohcomprises contacting said crude gas 'with-a liquor containing hydratedtammonia,

whereby the ammonia, hydrogen suld and carbon dioxid of said crude gas are absorbed by said liquor, withdrawing said liquor from Contact. with said gas, subject# ing said liquor touheating,` whereby ammonia, hydrogen suliid and carbon dioxid Lire evolved from said liquor', oxidizingsaid hydrogen sulid, to water vapor. and oxids ot sulfur in the presence ot' said ammonia and carbon dioxid, whereby the said water vapor and oxids of sulfur combine with said ammonia to form sulite and sulfate of ammonium, and separating the ammonium salts formed from the residual gases.

The process of recovering oxidized sulfur salts of ammonium from crude gas which comprises contacting said gas with a liquor containing a suiticient proportion ot tree ammonia to combine with the uncomhincd acid constituents of said crude gas, whereby the ammonia, hydrogen suli'id and carbon dioxid ot' said crude gas are absorbed hy said liquor, withdrawing said liquor trom contact with said gas, subjecting said liquor to heating at a-teniperature above the dissociation tenilwrature oi the volatiliizahle ammonium salts ot said liquor but below the boiling temperature ot said liquor, whereby a major portion ot the hydrogen sullid and carbon dioxid and a minor portion of the ammonia of said liquor are distilled therefrom, mixing with the said distilled gases sutlicient oxygen to oxidizc the contained hydrogen sultid ot said distilled gases, contacting such gas mixture with a catalytic material capable ot' reacting to transfer saidoxygen to the elements of said hydrogen suliid, whereby the latter is oxidized to water and oxid of sulfur which, in thepresenceof said ammonia, combine with the same to form oxidized sult'ur salts of ammonium. y

14. The process of recoveringoxidized Sulfur salts of ammonium from crude gas which comprises contacting said crude gas with a liquor containing hydrated ammonia., whereby the ammonia, hydrogen sulid and otherimpurities of said crude gas are absorbed by said liquor, withdrawing said liquor from contact with said gas, subjecting said liquor to heating at a temperature between 190 and 200o Fah., whereby a major proportion of the hydrogen sulid and other acid gases and a minor proportion of the ammonia of said liquor are distilled therefrom. mixing with Vthe said distilled gases sutlieient oxygen to oxidize the contained hydrogen sulfid of said distilled gases, contacting such gas mixture with oxid of iron maintained ata temperature such that it will react to transfer the oxygen of said gas mixture to the said hydrogen sulfid, whereb the latter is oxidized to water and oxi of sulfur, which in the presence of the ammonia said gas mixture sulfur salt of ammonium from crude gas 5 which comprises contacting said gas with a liquor containing free ammonia, whereby l the ammonia, hydrogen sulfid and other con` stitucnts of said crude gas are absorbed byV said li uor to form foul liquor, Withdrawving sai foul liquor from contact With said gas, subjecting said foul liquor to heating at a temperature below.the boiling point of said liquor butabove the dissociation tcmperature of the volatilizable ammonium salts of said liquor, whereby a major portion of the said ammonium salts are dissociated with the elimination from said liquor ofa major proportion of its hydrogen sulfid and other acid gases and a minor proportion of its ammonia, vto form puried liquor, cooling the major portion of said purified liquor and contacting said purified liquor With a fresh portion of crude gas, subjecting the minor portion of said purified liquor to boiling to distil ofl" therefrom substantially 'af' of itsvolatilizable gases, cooling the boiled liquor and contacting the cooled liquor With a portion of crude gas after the latter has been contacted with said purified 30 liquor, mixing With the gases eliminated from said foul liquor sufficient oxygen to oxidize the hydrogen sulfid of said gases to water and sulfur dioxid, contacting such mixture With oxid of iron mai-ntained at a reactive temperature, whereby the oxygen in the said gas mixture is transferred to the said hydrogen suliid to oxidize the latter to Water, sulfur dioxid and Some sulfur trioxid, which products in the presence ofthe ammonia of said gas mixture combineoijith the ammonia to form ammonium sulfite and some ammonium sulfate, cooling the gases A after contacting them with said iron oxid f and removing the ammonium salts from the residual gases,

l 16. The process of recovering salt of ammonium from `crude gas which comprises contacting said gas with a purified ammonia liquor containing free ammonia, whereby the ammonia, the hydrogen sulfid and carbon dioxid of the crude gas are absorbed by said liquor to form foul liquor, ivithdrawing said foul liquor from contact With said gas, subjecting said foul liquor to heating by hot purified liquor, further heating said foul liquor at a temperature below the boiling point of the same until a major port-ion of the ammonium salts of said liquor are dissociated with the elimination from said liquor of the major portion of its acid coinnents and a minor portion of its ammonia; o form purified liquor, cooling thev major portionof said purified liquor 'by a fresh portion of foul-liquor, and contacting the cooled purified liquor. with a fresh portion of crude gas, subjecting the minor portion of said purified liquor to boiling to distil Y olf therefrom substantially all 'of its volatilizable gases, contacting such distilled gases with another portion of purified liquor, and adding the unabsorbed portion of such distilled gases to the 'gases eliininated from another portion of said foul liquor, subjecting aifraction of the boiled minor portion of said purified liquor to fur- -ther boiling with lime to expel its fixed ammonia, adding the ammonia so expelledto the ammonia distilled from the minor poi'- tion of said purified liquor, Cooling the residual portion of the boiled 'minor portion of said purified liquor and contacting itwith, another portion of crude gaslafter the latter has been contacted With sai liquor and then -adding it to the purified liquor to be used to scrub a fresh portion of purified crude gas, mixing with the gases eliminated from said foul liquor a sufficient proportion. of air to furnish oxygen to oxidize somewhat more4 of the hydrogen sulfid of said gases than the proportion equivalent to the ammonia content of said gases;'contactiiig said gaseous mixture with oxid of iron. maintained at a temperature such that'lt.

will react to transfer the oxygen of the gas mixture to said hydrogen sulfid, thereby oxidizing the latter to Water and sulfur dioxid chiefly which, in the presence of the ammonia of said mixture, react with said ammonia to 'form ammonium sulfite, cliieiiy, cooling the gas mixture after the latter has been contacted with said iron oxid, and separating the oxidized sulfur salt of ammonium formed from the residual gases.

Signed at New York city in the county of New York and State of New York this 12th day of February A. D. 1910.

HENRY L. DOHERT Y.

Nitnessesz L. G. COLEMAN, THos. I. CARTER. 

